This invention relates to apparatus for monitoring particulate matter in fluids.
The occurrence of particulate matter or debris within a fluid can in many engineering situations create problems. For example if a lubricating fluid or oil is contaminated to a sufficient level by particulate matter it may not continue to act as a lubricant. Alternatively, the increase in debris in the fluid can produce malfunction of a device in which the fluid is used, for example air used in a combustion engine. Consequently, it can be useful to know when the unacceptable level is attained or approached. Hitherto, a filter has been provided in a return loop, say, of a lubricating system and the pressure drop across the filter has been used to activate an alarm system when the pressure exceeds a predetermined level as a consequence of matter trapped by the filter, for example as disclosed in the U.S. Pat. No. 4,117,717.
The above mentioned system may be adequate to warn of unacceptable levels of particulate matter or contaminants. Nevertheless, it does not give information which could correlate between the debris source and the wear and damage within the system. Also it does not give an indication of the build-up pattern of the contaminants. Consequently, it is not possible to determine whether debris has accumulated slowly or within a short period of time, the latter indicating a recent major debris source, probably as a result of a fault. Although the sample collected by the filter can be analysed, the analysis does not provide a pattern of the accumulation of debris prior to activation of the alarm system. Therefore, it is difficult to isolate the cause of the debris.